Cancer is a common disease that affects many people. Often cancer is not identified until severe symptoms manifest. For common types of cancer, there are screening techniques to identify patients who may have cancer. But, such techniques are often unreliable or subject a patient to radiation. For many other types of cancers, there are no effective screening techniques.
Loss of heterozygosity (LOH) has been detected for a particular locus in the circulating DNA of patients suffering from lung, and head and neck cancers (Chen X Q, et al. Nat Med 1996; 2: 1033-5; Nawroz H, et al. Nat Med 1996; 2: 1035-7). However, such techniques have been hindered by a relative small amount of LOH that has been detectable from examining a particular locus. Even when using digital PCR, these methods still suffer from an inability to detect small amounts of LOH. Moreover, such techniques have still been limited to investigating a particular locus that is known to occur in a specific type of cancer. Thus, a screening for cancer in general has not been possible or effective.
Besides screening for an existence of cancer, current techniques are also lacking for providing a prognosis of a patient with cancer and for monitoring the effects of treatment (e.g. recovery after surgery or chemotherapy or immunotherapy or targeted therapy). Such techniques are often expensive (e.g. imaging techniques), inaccurate, ineffective, insensitive or may subject the patient to the radiation used for imaging techniques.
Accordingly, it is desirable to provide new techniques for screening, prognosticating, and monitoring a patient for cancer.